The present invention relates to a method and a device for reducing damage caused by an accident after a primary accident, in which in particular a vehicle driver is unable to bring the vehicle that has had an accident into a safe position.
Previous systems of active and passive safety aim at a primary accident. As the primary accident is taking place, the driver is usually in full control of the vehicle. Thus, he is in a position to actively influence the behavior of the vehicle.
In order to avoid primary accidents, devices which automatically counteract instabilities of the vehicle have been integrated into the vehicles. These devices comprise a large number of driving stability control systems. The term ‘driving stability control’ combines five principles of influencing the driving behavior of a vehicle by means of predeterminable pressures or brake forces in or at individual wheel brakes and by means of intervention into the engine management of the driving engine. These systems refer to brake slip control (ABS) which is meant to prevent individual wheels from locking during a braking operation, traction control (TCS) preventing the spinning of the driven wheels, electronic brake force distribution (EBD) for controlling the relationship between the brake force on the front and rear axles of the vehicle, roll-over prevention (ARP) to prevent roll-over of a vehicle about its longitudinal axis, and yaw torque control (ESP) which safeguards stable driving conditions when the vehicle yaws about its vertical axis.
A vehicle is defined in this connection as a motor vehicle with four wheels, which is equipped with a hydraulic, an elector-hydraulic or electro-mechanical brake system. In the hydraulic brake system, brake pressure can be built up by the driver by means of a pedal-actuated master cylinder, while the electro-hydraulic and electromechanical brake systems build up a brake force in response to the sensed braking request of the driver. Hereinbelow, reference is made to a hydraulic brake system. Each wheel has a brake, with which one inlet valve and one outlet valve each is associated. The wheel brakes communicate with the master cylinder by way of the inlet valves, while the outlet valves lead to a pressureless tank or to a low-pressure accumulator. Finally, there also is an auxiliary pressure source, which is able to build up a pressure in the wheel brakes regardless of the position of the brake pedal. The inlet and outlet valves can be electromagnetically actuated for pressure control in the wheel brakes.
To detect states in the dynamics of the vehicle movement, there are four speed sensors, one per wheel, at least one yaw rate meter, one lateral acceleration meter, optionally one longitudinal acceleration sensor, and at least one pressure sensor for the brake pressure generated by the brake pedal. The pressure sensor may be replaced with a pedal travel or pedal force meter if the auxiliary pressure source is arranged such that a brake pressure built up by the driver is not distinguishable from that of the auxiliary pressure source.
In driving stability control, the driving behavior of a vehicle is influenced such that the driver will be better able to master the vehicle in critical situations. A critical situation is defined herein as an unstable driving condition in which, in the extreme case, the vehicle does not follow the driver's instructions. The function of driving stability control is consequently to impart to the vehicle the behavior desired by the driver in such situations within the physical limits.
While the longitudinal slip of the tires on the road surface is mainly of significance for the brake slip control system, the traction slip control system and the electronic brake force distribution system, the yaw torque control system (YTC) also involves additional variables, e.g., the yaw rate and the tire slip angle velocity. Anti-rollover control systems generally evaluate variables relating to lateral acceleration or roll variables (DE 196 32 943 A1).
In addition to driving stability control systems, assist and safety systems are provided in vehicles at an increasing rate, analyzing traffic situations based on an ambience sensor system and automatically adapting the vehicle speed to the detected driving situation depending on the detected ambience, or initiating the active safety systems because an accident is forecast due to a detected risk potential.
However, consequential accidents may happen subsequent to a primary accident in a number of scenarios. Hence, the vehicle which has had an accident presents a high risk to both its occupants as well as to other traffic participants, what is due to its further uncontrolled movement pattern until standstill. This risk is not mastered by the state of the art. Once the driver has lost control of the vehicle after the primary accident, because he lost consciousness or suffered a shock, not even an ESP system will make it possible for him to bring the vehicle safely to standstill or steer it safely around possible obstacles.
In view of the above, an object of the invention is to design the vehicle systems in such a manner that an appropriate control intervention is carried out before the vehicle which has had the accident causes consequential accidents.